This invention relates to a vacuum insulating glass (IG) unit, and a method of making the same. More particularly, this invention relates to a vacuum IG unit including a peripheral seal including at least one spacer therein.
Vacuum IG units are known in the art. For example, see U.S. Pat. Nos. 5,664,395, 5,657,607, 5,891,536 and 5,902,652, the disclosures of which are all hereby incorporated herein by reference.
Prior art FIGS. 1-2 illustrate a conventional vacuum IG unit. IG unit 1 includes two spaced apart sheets of glass 2 and 3 which enclose an evacuated or low pressure space 11 therebetween. Glass sheets 2 and 3 are interconnected by peripheral or edge seal of fused solder glass 4 and an array of support pillars 5.
Pump out tube 6 is sealed by solder glass 7 to an aperture or hole which passes from an interior surface of glass sheet 2 to the bottom of recess 9. Cavity 8 in sheet 3 accommodates the stump of tube 6. A vacuum is attached to tube 6 (prior to the tube being sealed) so that the interior cavity 11 between sheets 2 and 3 can be evacuated to create a low pressure area. After evacuation, tube 6 is melted to seal the vacuum.
As illustrated in FIGS. 1-2, spacers or pillars 5 are typically provided between the glass sheets 2 and 3 through the viewing area of the unit, but not at edges thereof where peripheral or edge seal 4 is located. This results in the thickness of gap or space 11 potentially varying from one thickness near the edge(s) of the glass sheet(s) to a different thickness near the center where more spacers are provided. In other words, there is a potential for substantial undesirable gap variation at the edges relative to center areas of the unit. If the gap or thickness of the low pressure space 11 between the substrates is lower or higher at the edge than proximate the center of the unit, then the edge seal and/or glass substrate(s) can have higher stress than if the gap is approximately equal throughout the unit. The higher the stress, the more likely it is for either of the glass substrates to crack or break, and the more likely it is for the edge seal to delaminate.
It is apparent from the above that there exists a need in the art for a vacuum IG unit, and corresponding method of making the same, designed so as to reduce the potential for significant gap variation of the thickness of the space between the two substrates.
This invention will now be described with respect to certain embodiments thereof, accompanied by certain illustrations.